A wide variety of electronic devices are designed with displays to meet consumer demands. In some instances, the displays play a supporting role in enhancing functionality. These displays are typically found in mobile phones, music players, and cameras. In other instances, the displays are the primary feature. These displays are included in televisions, computers, and projection systems.
One display technology that has demonstrated superior performance is liquid-crystal-on-silicon (LCOS). An LCOS display generates gray scale images based on the varying reflectance that results from field-controlled polarization of liquid crystal. These displays tend to be low-power, high-resolution devices that can be manufactured at relatively low cost and in many sizes. They are also structurally different from other liquid crystal display (LCD) technologies. For example, thin-film-transistor (TFT) LCDs use glass back planes and back-side light sources, whereas LCOS displays use silicon back planes and front-side light sources. As a result, LCOS displays can be integrated into standard semiconductor processes, which is attractive from a manufacturing standpoint.
FIG. 1 shows, in cross-section, an example of a LCOS device for generating images in a display system. The device includes a ceramic bottom plate 1, a silicon back plane 2 on the ceramic plate, and a glass front plane 6 arranged over and in parallel with the back plane. The device also includes a liquid crystal layer 4 between the front and back planes. Pixels are activated by electrodes 3 and 5 disposed below and above the liquid crystal layer. The lower electrode (nearest the back plane) has a mirrored surface for reflecting light from a front-side light source.
Although LCOS devices such as shown in FIG. 1 are widely available, they have proven unsatisfactory in terms of their ability to achieve high-yield production with reliable results. Moreover, significant challenges exist in the area of silicon and liquid crystal material joint assembly.